﻿#include <linux/module.h>
#include <linux/poll.h>

#include <linux/device.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/miscdevice.h>
#include <linux/mutex.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/timer.h>
#include <linux/tty.h>

struct gpio_desc {
  int gpio;
  int irq;
  char name[128];
  int key;
  struct timer_list key_timer;
};

static struct gpio_desc *gpios;
static int count;

/* 主设备号                                                                 */
static int major = 0;
static struct class *gpio_class;

/* 环形缓冲区 */
#define BUF_LEN 128
static int g_keys[BUF_LEN];
static int r, w;

struct fasync_struct *button_fasync;

#define NEXT_POS(x) ((x + 1) % BUF_LEN)

static int is_key_buf_empty(void) { return (r == w); }

static int is_key_buf_full(void) { return (r == NEXT_POS(w)); }

static void put_key(int key) {
  if (!is_key_buf_full()) {
    g_keys[w] = key;
    w = NEXT_POS(w);
  }
}

static int get_key(void) {
  int key = 0;
  if (!is_key_buf_empty()) {
    key = g_keys[r];
    r = NEXT_POS(r);
  }
  return key;
}

static DECLARE_WAIT_QUEUE_HEAD(gpio_wait);

// static void key_timer_expire(struct timer_list *t)
static void key_timer_expire(struct timer_list *data) {
  /* data ==> gpio */
  // struct gpio_desc *gpio_desc = from_timer(gpio_desc, t, key_timer);
  struct gpio_desc *gpio_desc = (struct gpio_desc *)data;
  int val;
  int key;

  val = gpio_get_value(gpio_desc->gpio);

  // printk("key_timer_expire key %d %d\n", gpio_desc->gpio, val);
  key = (gpio_desc->key) | (val << 8);
  put_key(key);
  wake_up_interruptible(&gpio_wait);
  kill_fasync(&button_fasync, SIGIO, POLL_IN);
}

/* 实现对应的open/read/write等函数，填入file_operations结构体 */
static ssize_t gpio_drv_read(struct file *file, char __user *buf, size_t size,
                             loff_t *offset) {
  // printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  int err;
  int key;

  if (is_key_buf_empty() && (file->f_flags & O_NONBLOCK))
    return -EAGAIN;

  wait_event_interruptible(gpio_wait, !is_key_buf_empty());
  key = get_key();
  err = copy_to_user(buf, &key, 4);

  return 4;
}

static ssize_t gpio_drv_write(struct file *file, const char __user *buf,
                              size_t size, loff_t *offset) {
  unsigned char ker_buf[2];
  int err;

  if (size != 2)
    return -EINVAL;

  err = copy_from_user(ker_buf, buf, size);

  if (ker_buf[0] >= count)
    return -EINVAL;

  gpio_set_value(gpios[ker_buf[0]].gpio, ker_buf[1]);
  return 2;
}

static unsigned int gpio_drv_poll(struct file *fp, poll_table *wait) {
  // printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  poll_wait(fp, &gpio_wait, wait);
  return is_key_buf_empty() ? 0 : POLLIN | POLLRDNORM;
}

static int gpio_drv_fasync(int fd, struct file *file, int on) {
  if (fasync_helper(fd, file, on, &button_fasync) >= 0)
    return 0;
  else
    return -EIO;
}

/* 定义自己的file_operations结构体 */
static struct file_operations gpio_key_drv = {
    .owner = THIS_MODULE,
    .read = gpio_drv_read,
    .write = gpio_drv_write,
    .poll = gpio_drv_poll,
    .fasync = gpio_drv_fasync,
};

static irqreturn_t gpio_key_isr(int irq, void *dev_id) {
  struct gpio_desc *gpio_desc = dev_id;
  printk("gpio_key_isr key %d irq happened\n", gpio_desc->gpio);
  mod_timer(&gpio_desc->key_timer, jiffies + HZ / 5);
  return IRQ_HANDLED;
}

/* 在入口函数 */
static int gpio_drv_probe(struct platform_device *pdev) {
  int err = 0;
  int i;
  struct device_node *np = pdev->dev.of_node;
  struct resource *res;

  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);

  /* 从platfrom_device获得引脚信息
   * 1. pdev来自c文件
   * 2. pdev来自设备树
   */

  if (np) {
    /* pdev来自设备树 : 示例
reg_usb_ltemodule: regulator@1 {
compatible = "100ask,gpiodemo";
gpios = <&gpio5 5 GPIO_ACTIVE_HIGH>, <&gpio5 3 GPIO_ACTIVE_HIGH>;
};
    */
    count = of_gpio_count(np);
    if (!count)
      return -EINVAL;

    gpios = kmalloc(count * sizeof(struct gpio_desc), GFP_KERNEL);
    for (i = 0; i < count; i++) {
      gpios[i].gpio = of_get_gpio(np, i);
      sprintf(gpios[i].name, "%s_pin_%d", np->name, i);
    }
  } else {
    /* pdev来自c文件
    static struct resource omap16xx_gpio3_resources[] = {
            {
                            .start  = 115,
                            .end    = 115,
                            .flags  = IORESOURCE_IRQ,
            },
            {
                            .start  = 118,
                            .end    = 118,
                            .flags  = IORESOURCE_IRQ,
            },		};
    */
    count = 0;
    while (1) {
      res = platform_get_resource(pdev, IORESOURCE_IRQ, count);
      if (res) {
        count++;
      } else {
        break;
      }
    }

    if (!count)
      return -EINVAL;

    gpios = kmalloc(count * sizeof(struct gpio_desc), GFP_KERNEL);
    for (i = 0; i < count; i++) {
      res = platform_get_resource(pdev, IORESOURCE_IRQ, i);
      gpios[i].gpio = res->start;
      sprintf(gpios[i].name, "%s_pin_%d", pdev->name, i);
    }
  }

  for (i = 0; i < count; i++) {
    gpios[i].irq = gpio_to_irq(gpios[i].gpio);

    timer_setup(&gpios[i].key_timer, key_timer_expire,
                (unsigned long)&gpios[i]);
    // timer_setup(&gpios[i].key_timer, key_timer_expire, 0);
    gpios[i].key_timer.expires = ~0;
    add_timer(&gpios[i].key_timer);
    err = request_irq(gpios[i].irq, gpio_key_isr,
                      IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
                      "100ask_gpio_key", &gpios[i]);
  }

  /* 注册file_operations 	*/
  major =
      register_chrdev(0, "100ask_gpio_key", &gpio_key_drv); /* /dev/gpio_desc */

  gpio_class = class_create(THIS_MODULE, "100ask_gpio_key_class");
  if (IS_ERR(gpio_class)) {
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    unregister_chrdev(major, "100ask_gpio_key");
    return PTR_ERR(gpio_class);
  }

  device_create(gpio_class, NULL, MKDEV(major, 0), NULL,
                "100ask_gpio"); /* /dev/100ask_gpio */

  return err;
}

/* 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数
 */
static int gpio_drv_remove(struct platform_device *pdev) {
  int i;

  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);

  device_destroy(gpio_class, MKDEV(major, 0));
  class_destroy(gpio_class);
  unregister_chrdev(major, "100ask_gpio_key");

  for (i = 0; i < count; i++) {
    free_irq(gpios[i].irq, &gpios[i]);
    del_timer(&gpios[i].key_timer);
  }

  return 0;
}

static const struct of_device_id gpio_dt_ids[] = {
    {
        .compatible = "100ask,gpiodemo",
    },
    {/* sentinel */}};

static struct platform_driver gpio_platform_driver = {
    .driver =
        {
            .name = "100ask_gpio_plat_drv",
            .of_match_table = gpio_dt_ids,
        },
    .probe = gpio_drv_probe,
    .remove = gpio_drv_remove,
};

static int __init gpio_drv_init(void) {
  /* 注册platform_driver */
  return platform_driver_register(&gpio_platform_driver);
}

static void __exit gpio_drv_exit(void) {
  /* 反注册platform_driver */
  platform_driver_unregister(&gpio_platform_driver);
}

/* 7. 其他完善：提供设备信息，自动创建设备节点 */

module_init(gpio_drv_init);
module_exit(gpio_drv_exit);

MODULE_LICENSE("GPL");
